1. Field of the Invention
The present invention is generally directed to a nodular graphite cast iron. In particular, the present invention is directed to a nodular graphite cast iron with high strength and high toughness.
2. Discussion of the Background
In general, automotive products having a thin and lightweight structure are desired. Because many automotive products are formed from nodular graphite cast iron, this desire translates into a need for nodular graphite cast iron to be strengthened, which will allow automotive products to be made thinner and more lightweight.
However, when conventional nodular graphite cast iron is strengthened so that its tensile strength reaches 700 MPa, its impulse value becomes 5 J/cm2 or less. Although this conventional nodular graphite cast iron has high tensile strength, its low toughness limits its use in making thin, lightweight automotive parts.
There is a need for a nodular graphite cast iron combining both high strength and high toughness.